For almost a decade, the two major ferry operators in the Cape and Islands were united in trenchant opposition to Cape Wind. Suddenly though, one operator sees the wind farm as a major tourism opportunity, while the other maintains it is a navigational hazard.

The one that changed position was Hy-Line Cruises, which announced this week that it was partnering with Cape Wind to develop eco-themed tours of the 130-turbine wind farm in Nantucket Sound, both during construction and operation.

Cape Wind has gained all the necessary approvals, but opponents still are pursuing a number of legal challenges.

Hy-Line, which once said that the construction would court maritime disaster, now is planning on the assumption that those challenges will fail and development will begin later this year.

At a media conference on Monday, plans were announced for a joint venture between the ferry company and the wind developer, including a new eco-friendly visitor center designed to “educate visitors of all ages about the history of the Cape Wind project and energy use on Cape Cod, the U.S. and around the world.”

There would be particular emphasis on local history, including the transition from windmills to whale oil, to fossil fuels “and the transition to a clean energy economy led by the citizens of Cape Cod and Massachusetts.”

In addition, Hy-Line plans to develop a new hybrid vessel to conduct the tours, possibly to be built in Massachusetts. The boat line also said it intended to develop with Cape Cod Community College “a curriculum of credit and noncredit courses” to train students for work both in the visitor center and on the cruises.

They also were working with the Cape Cod Regional Transit Authority to tie into its network, using “green” shuttle buses to service offsite parking.

But, as Hy-Line spokesman Martin Reilly later explained, the timing of it all is dependent in the first instance on what happens in the courts, and then on tourist numbers.

“Initially it will start with one [149 passenger] vessel, and that first vessel may not be green. But hopefully as it grows, we will be adding more vessels.”

Mr. Reilly noted the experience in Denmark, where such tours are immensely popular. “Eco tours are one of the largest growth sectors of the tourism industry,” he said.

He also said the change in Hy-Line’s position on Cape Wind was not as sudden as it appeared.

“Approximately 15 months ago Hy-Line had a meeting with Cape Wind —– for the very first time a direct meeting, as opposed to the adversarial perspective which was the previous nature of all exchanges on this issues.

“It was held at the Hy-Line offices, where the owners of Hy-Line, the Scudder family, as a prerequisite for making a decision on whether or not they would be part of litigation, laid out the navigational charts and went through their ferry routes with the Cape Wind people.

“As the discussion progressed, they felt increasingly confident they could safely navigate around it. So they decided not to be part of the litigation, to continue to work with the Coast Guard and Cape Wind.”

Together they had worked out ways to mitigate the impact of the find farm on navigation.

However, the Steamship Authority, the largest operator between the Cape and Islands, continues to have big concerns about the navigational impacts of the Cape Wind project, and the general manager of the authority, Wayne Lamson, said this week that he remained in the dark about any new mitigation measures.

“I don’t know what Hy-Line is talking about when they say they’ve met with the Coast Guard and Cape Wind and they’ve mitigated their concerns. Apparently they’re aware of something the Steamship Authority is not.

“Hopefully at some point before the turbines are constructed we’ll get a better sense of what steps are to be taken. As of now they haven’t shared it with us,” he said.

The wind farm development posed a danger because of radar interference and because it would result in greater congestion of the ferry routes, he said.

“Recreational boaters will likely be staying out of there [the wind farm site], at least in foggy weather, so they’ll be more in the ferry routes,” he said.

The siting of the wind farm presented a particular problem for SSA boats during bad weather, he said.

“When we have to do tacking maneuvers in bad conditions, we do go over there [into parts of Horseshoe Shoal, where the turbines will be].

“If that is taken away from us, it may be that we have to cancel more trips in future, because we simply can’t operate safely in bad weather.”

Mr. Lamson also predicted problems on those rare occasions, maybe once in 10 years, when ice formed on the Sound.

“In the past the Coast Guard has come to our aid when we’ve had issues with ice. We get an icebreaker out of Maine.

“What is going to happen once these turbines are built? I don’t see how the sea ice can be broken up so it doesn’t impede navigation,” he said.

“I don’t see anything about their icebreaking in their operational plan. I don’t see anything about what impact it will have on our operations while they are laying the cable from the turbines into Yarmouth.”

“The channel is quite narrow and we don’t know what type of barges or other equipment is going to be required. It’s going to displace a substantial amount of the bottom sediment as they proceed. We don’t know how that will affect the bottom contour going forward and how much additional dredging might be required,” Mr. Lamson said.